/*
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 */

/*
 *
 *
 *
 *
 *
 * Written by Doug Lea with assistance from members of JCP JSR-166
 * Expert Group and released to the public domain, as explained at
 * http://creativecommons.org/publicdomain/zero/1.0/
 */

package java.util.concurrent.atomic;

import java.util.function.IntUnaryOperator;
import java.util.function.IntBinaryOperator;
import sun.misc.Unsafe;

/**
 * An {@code int} value that may be updated atomically.  See the
 * {@link java.util.concurrent.atomic} package specification for
 * description of the properties of atomic variables. An
 * {@code AtomicInteger} is used in applications such as atomically
 * incremented counters, and cannot be used as a replacement for an
 * {@link java.lang.Integer}. However, this class does extend
 * {@code Number} to allow uniform access by tools and utilities that
 * deal with numerically-based classes.
 *
 * @author Doug Lea
 * @since 1.5
 */
public class AtomicInteger extends Number implements java.io.Serializable {

  private static final long serialVersionUID = 6214790243416807050L;

  // setup to use Unsafe.compareAndSwapInt for updates
  private static final Unsafe unsafe = Unsafe.getUnsafe();
  private static final long valueOffset;

  static {
    try {
      valueOffset = unsafe.objectFieldOffset
          (AtomicInteger.class.getDeclaredField("value"));
    } catch (Exception ex) {
      throw new Error(ex);
    }
  }

  private volatile int value;

  /**
   * Creates a new AtomicInteger with the given initial value.
   *
   * @param initialValue the initial value
   */
  public AtomicInteger(int initialValue) {
    value = initialValue;
  }

  /**
   * Creates a new AtomicInteger with initial value {@code 0}.
   */
  public AtomicInteger() {
  }

  /**
   * Gets the current value.
   *
   * @return the current value
   */
  public final int get() {
    return value;
  }

  /**
   * Sets to the given value.
   *
   * @param newValue the new value
   */
  public final void set(int newValue) {
    value = newValue;
  }

  /**
   * Eventually sets to the given value.
   *
   * @param newValue the new value
   * @since 1.6
   */
  public final void lazySet(int newValue) {
    unsafe.putOrderedInt(this, valueOffset, newValue);
  }

  /**
   * Atomically sets to the given value and returns the old value.
   *
   * @param newValue the new value
   * @return the previous value
   */
  public final int getAndSet(int newValue) {
    return unsafe.getAndSetInt(this, valueOffset, newValue);
  }

  /**
   * Atomically sets the value to the given updated value
   * if the current value {@code ==} the expected value.
   *
   * @param expect the expected value
   * @param update the new value
   * @return {@code true} if successful. False return indicates that the actual value was not equal
   * to the expected value.
   */
  public final boolean compareAndSet(int expect, int update) {
    return unsafe.compareAndSwapInt(this, valueOffset, expect, update);
  }

  /**
   * Atomically sets the value to the given updated value
   * if the current value {@code ==} the expected value.
   *
   * <p><a href="package-summary.html#weakCompareAndSet">May fail
   * spuriously and does not provide ordering guarantees</a>, so is
   * only rarely an appropriate alternative to {@code compareAndSet}.
   *
   * @param expect the expected value
   * @param update the new value
   * @return {@code true} if successful
   */
  public final boolean weakCompareAndSet(int expect, int update) {
    return unsafe.compareAndSwapInt(this, valueOffset, expect, update);
  }

  /**
   * Atomically increments by one the current value.
   *
   * @return the previous value
   */
  public final int getAndIncrement() {
    return unsafe.getAndAddInt(this, valueOffset, 1);
  }

  /**
   * Atomically decrements by one the current value.
   *
   * @return the previous value
   */
  public final int getAndDecrement() {
    return unsafe.getAndAddInt(this, valueOffset, -1);
  }

  /**
   * Atomically adds the given value to the current value.
   *
   * @param delta the value to add
   * @return the previous value
   */
  public final int getAndAdd(int delta) {
    return unsafe.getAndAddInt(this, valueOffset, delta);
  }

  /**
   * Atomically increments by one the current value.
   *
   * @return the updated value
   */
  public final int incrementAndGet() {
    return unsafe.getAndAddInt(this, valueOffset, 1) + 1;
  }

  /**
   * Atomically decrements by one the current value.
   *
   * @return the updated value
   */
  public final int decrementAndGet() {
    return unsafe.getAndAddInt(this, valueOffset, -1) - 1;
  }

  /**
   * Atomically adds the given value to the current value.
   *
   * @param delta the value to add
   * @return the updated value
   */
  public final int addAndGet(int delta) {
    return unsafe.getAndAddInt(this, valueOffset, delta) + delta;
  }

  /**
   * Atomically updates the current value with the results of
   * applying the given function, returning the previous value. The
   * function should be side-effect-free, since it may be re-applied
   * when attempted updates fail due to contention among threads.
   *
   * @param updateFunction a side-effect-free function
   * @return the previous value
   * @since 1.8
   */
  public final int getAndUpdate(IntUnaryOperator updateFunction) {
    int prev, next;
    do {
      prev = get();
      next = updateFunction.applyAsInt(prev);
    } while (!compareAndSet(prev, next));
    return prev;
  }

  /**
   * Atomically updates the current value with the results of
   * applying the given function, returning the updated value. The
   * function should be side-effect-free, since it may be re-applied
   * when attempted updates fail due to contention among threads.
   *
   * @param updateFunction a side-effect-free function
   * @return the updated value
   * @since 1.8
   */
  public final int updateAndGet(IntUnaryOperator updateFunction) {
    int prev, next;
    do {
      prev = get();
      next = updateFunction.applyAsInt(prev);
    } while (!compareAndSet(prev, next));
    return next;
  }

  /**
   * Atomically updates the current value with the results of
   * applying the given function to the current and given values,
   * returning the previous value. The function should be
   * side-effect-free, since it may be re-applied when attempted
   * updates fail due to contention among threads.  The function
   * is applied with the current value as its first argument,
   * and the given update as the second argument.
   *
   * @param x the update value
   * @param accumulatorFunction a side-effect-free function of two arguments
   * @return the previous value
   * @since 1.8
   */
  public final int getAndAccumulate(int x,
      IntBinaryOperator accumulatorFunction) {
    int prev, next;
    do {
      prev = get();
      next = accumulatorFunction.applyAsInt(prev, x);
    } while (!compareAndSet(prev, next));
    return prev;
  }

  /**
   * Atomically updates the current value with the results of
   * applying the given function to the current and given values,
   * returning the updated value. The function should be
   * side-effect-free, since it may be re-applied when attempted
   * updates fail due to contention among threads.  The function
   * is applied with the current value as its first argument,
   * and the given update as the second argument.
   *
   * @param x the update value
   * @param accumulatorFunction a side-effect-free function of two arguments
   * @return the updated value
   * @since 1.8
   */
  public final int accumulateAndGet(int x,
      IntBinaryOperator accumulatorFunction) {
    int prev, next;
    do {
      prev = get();
      next = accumulatorFunction.applyAsInt(prev, x);
    } while (!compareAndSet(prev, next));
    return next;
  }

  /**
   * Returns the String representation of the current value.
   *
   * @return the String representation of the current value
   */
  public String toString() {
    return Integer.toString(get());
  }

  /**
   * Returns the value of this {@code AtomicInteger} as an {@code int}.
   */
  public int intValue() {
    return get();
  }

  /**
   * Returns the value of this {@code AtomicInteger} as a {@code long}
   * after a widening primitive conversion.
   *
   * @jls 5.1.2 Widening Primitive Conversions
   */
  public long longValue() {
    return (long) get();
  }

  /**
   * Returns the value of this {@code AtomicInteger} as a {@code float}
   * after a widening primitive conversion.
   *
   * @jls 5.1.2 Widening Primitive Conversions
   */
  public float floatValue() {
    return (float) get();
  }

  /**
   * Returns the value of this {@code AtomicInteger} as a {@code double}
   * after a widening primitive conversion.
   *
   * @jls 5.1.2 Widening Primitive Conversions
   */
  public double doubleValue() {
    return (double) get();
  }

}
